The speed of data communications networks has been increasing steadily and substantially over the past several decades, requiring newly designed components to enable the networks to operate at these new higher speeds. As the speed of networks increases, the frequency at which electrical signals in these networks are communicated increases, and physical wiring paths within the network, which presented no problems at lower frequencies, can become antennae that broadcast and receive electromagnetic radiation and cause errors in the data being communicated. This unwanted coupling of signals from one communication path to another is known as “crosstalk” and degrades the overall performance of the network. Unwanted crosstalk can occur between any proximate electrically conductive paths that physically form parts of the network, such as individual pairs of data signals within a given communications cable, between or among nearby communications cables, and within connectors used to connect cables to desired electronic components, such as routers and network switches, within the network.
FIG. 1 is a diagram illustrating a portion of a conventional communications network 100 including a typical communications channel 101. The channel 101 includes a communications outlet 102 into which a communications plug 104 of a cable 106 is inserted to thereby connect a computer system 108 to the communications network 100. The communications outlet 102 fits within an opening 110 of a wall plate 112 to expose an aperture 114 in the communications outlet into which the plug 104 is inserted. Electrical signals are then communicated to and from the computer system 108 through the cable 106, plug 104, outlet 102, and a cable 116. The cable 116 includes another communications outlet 118 on the other end of the cable, with the communications outlet 118 often being part of another network component such as a patch panel 120. A network switch 122 or other network component is connected to outlet 118 through a cable 124 and plug 126 to interconnect the communications channel 101 to other components in the network 100, as indicated by the arrow 127.
The cables 106 and 116, plug 104 and 126, and outlets 102 and 118 are standardized components that include specified numbers of electrically conductive components and arrangement of such components within the plugs and outlets. Where the system 100 utilizes the Ethernet communications standard, for example, data is communicated through four twisted-pairs of conductive wires in the cables 106, 116. The plugs 104, 126 and outlets 102, 118 likewise include four corresponding pairs of electrically conductive elements or paths, such as in RJ-45 outlet and plugs. For historical reasons, the physical arrangement of such electrically conductive components within the plugs 104 and 126 is such that unwanted crosstalk is generated between the pairs of such electrically conductive elements. The outlets 102, 118, are designed in such a manner as to nullify the crosstalk generated by the plugs. As the speed at which data is communicated increases, so does the frequency range of operation for all components of the communications channel 101, making nullification of the unwanted crosstalk more difficult to achieve for reasons understood by those skilled in the art. This arrangement of electrically conductive components for the plugs 104, 126 and outlets 102, 118 has nonetheless been retained even for current high-speed networks to provide compatibility between old and new network components.
As the speed or frequency at which networks operate continues to increase, crosstalk can become significant and can interfere with the proper operation of the network 100. There are generally two types of crosstalk. The first type of crosstalk occurs among the pairs of electrically conductive components within an individual communications channel 101 and is termed “internal crosstalk.” Internal crosstalk is the unwanted signals communicated from one pair to another within a single channel.
The second type of crosstalk is known as “alien crosstalk” and occurs between pairs of electrically conductive components in different communications channels 101. Alien crosstalk can be defined as unwanted signals communicated between pairs in different channels. Alien crosstalk can occur between most components of communications networks 100, and is particularly significant between those components which are physically located proximate to each other. For example, assume that nearby the cables 106, 116, plugs 104, 126, and outlets 102, 118 of the communications channel 101 of FIG. 1, there are several additional similar communications channels having corresponding components. This would typically be the case in the network 100.
One particular type of alien crosstalk is known as “modal alien crosstalk” and is initiated by the unequal electrical exposures of some of the electrically conductive components within the plugs 104, 126 to other comparable electrically conductive components. These unequal electrical exposures result in a modal conversion of signals that causes unwanted electromagnetic waves of a different mode to propagate in a given communications channel 101. These unwanted electromagnetic waves of a different mode can cause crosstalk in adjacent communications channels 101 that can interfere with the proper operation of such channels, particularly at the ever increasing frequencies at which networks operate. Since the outlets 102, 118 have conductors similarly arranged to those of the plug 104, 126 to be mechanically compatible, both the outlets and the plugs in a given channel cause modal conversion of signals. In addition, compensation circuitry used in the outlet to neutralize internal crosstalk can further add to the modal conversion of signals. Thus, both plugs and outlets contribute to the generation of modal alien crosstalk.
There is a need for improved communications outlets designed to neutralize the modal conversion of signals initiated in the plug, and reduce that generated in the outlet itself, without significantly increasing the complexity of manufacturing the outlet or its cost.